[notacoward]

I don't know Prometheus, but I would imagine the answer depends on just how many clients you have. Probably doesn't matter if you're talking just a few. If it's a lot, then separate instances can be very expensive in terms of operational complexity and waste due to resource fragmentation. Multi-tenancy is good for bringing both of those back under control. Is there something about Prometheus that would negate that?

[vladvasiliu]

For one, it doesn't really support authentication (although it's on the roadmap).

I'm no Prometheus expert, but since you're pretty much expected to be running a bunch of servers anyway, the operational complexity has to be handled even for just one client.

You do have a point on resource fragmentation, but IME Prometheus' resource usage is fairly predictable, so you could probably mitigate that to a point.